To supplement what elgyqc said, I put a 6-speed and 5-speed side by side to compare. A rough one-handed measurement while holding my cellphone in the other hand shows:
The 5-speed measures just over 7 inches from the face of the bell housing to axle center.
The 6-speed measures just over 8 inches from the face of the bell housing to axle center.
(note: the angle of the photo distorts the point I was measuring from)
If you are interested in a Cayman 6-speed transmission Woody held onto one for quite a while and may have it available cheap. His phone number has not changed, shown in the first post of this thread:
https://986forum.com/forums/boxsters-cayman-cars-sale-wanted/81718-2000-s-3-4-%2416-000-a.html